Cardiac arrhythmia is a condition in which the electrical activity of the heart is irregular or is faster or slower than normal. Cardiac arrhythmia may be classified by rate and/or mechanism. For instance, atrial fibrillation (AF) is the most common type of serious arrhythmia that involves a very fast and irregular contraction of the atria. Ventricular fibrillation (VF) is a condition in which there is uncoordinated contraction of the cardiac muscle of the ventricles in the heart. Myocardial ischemia (MI) is a type of arrhythmia that occurs when blood flow to the heart muscle is decreased by a partial or complete blockage of the heart's arteries. Myocardial infarction (commonly known as a heart attack) occurs when blood stops flowing properly to part of the heart and the heart muscle is injured due to not receiving enough oxygen. This can lead to irreversible scarring and necrosis of the muscle tissue, reducing the efficiency with which the heart can pump blood to the rest of the body and possibly leading to fatal cardiac arrhythmia.
Cardiac functional abnormality and arrhythmia usually slow down tissue performance (e.g., contracting and reperfusion) and reduce blood flow to regions of the heart. Cells respond by altering the action potentials. The changes in these individual cells manifest in electrograms during depolarization and repolarization, reducing signal energy (hyperkalemia or anoxia) or creating multi-phasic waveform, particularly distortions in the electrophysiological response morphology. Electrophysiological (EP) response and activity analysis is routinely used to manage such cardiac arrhythmias, disorders and irregularities. The 12-lead electrocardiogram (ECG) and multi-channel intra-cardiac electrograms (ICEG) are generally regarded as the diagnostic reference standard for evaluating cardiac rhythm and events.
Currently, waveform morphologies and time-domain parameter analysis, such as P wave, QRS complex, ST segment, T wave, are used for cardiac arrhythmia monitoring and identification. However, such analysis is sometimes subjective and time-consuming, and requires extensive medical expertise and clinical experience for accurate interpretation and proper cardiac rhythm management. Inaccurate and subjective evaluation and diagnosis may cause unexpected delays in cardiac rhythm management, such as drug delivery and emergency treatment.
Most traditional clinical methods and approaches are performed for qualitative testing and diagnosis of cardiac pathology (e.g., 0.1 mV of ST segment elevation for myocardial ischemia event detection). There is currently no known efficient, convenient, reliable and sensitive method to perform both quantitative and qualitative characterization and evaluation of cardiac signal waveform and morphology, especially for early detection and diagnosis of cardiac events. In addition, known clinical approaches may not be efficiently applicable and useful in some cases. For example, myocardial ischemia and infarction are usually detected by ST segment voltage deviation (e.g., 0.1 mV deviation). However, this method only works for surface ECG signals, but not intra-cardiac electrograms (ICEG) signals.
Accordingly, there exists a need to provide an improved framework to address these deficiencies and related problems.